
Perpdepog |
Fantasy Grounds has a Teamspeak server, but Discord works well, too. Teamspeak has better tools for me, since I use a second client for sound effects and sometimes swap over to a voice morpher. Last time I tried that in Discord switching away from the voice morpher didn't work.
Bit of a tangent, but what do you use for sound effects and voices and such? I've been thinking about trying that for my next game I GM, but don't feel like paying the subscription on Roll20 because my group all tends to share an account, but I don't believe that anyone but the account's owner can get access to the sound library.

Helmic |

Mumble would be the fancy way to do it. It's no harder than Teamspeak, but it's still involves getting a group of people of varying levels of tech literacy to connect to something they 100% are not going to keep running on their computer. But it does make things like voice morphers a lot easier to use if that's what you do.
Discord is probably the best option overall because you can create a link directly into the voice channel and your players will be dropped right in there, either through their browser or their downloaded client. Practically foolproof, and the text system isn't absolute trash garbage like TS3's. Makes it much easier to keep notes, schedule sessions, ping people, and otherwise organize your game when you're not playing. That it's completely free (as in no one has to pay for hosting) just makes it more tempting. For actual applications, Discord also has an overlay which can help clarify who's speaking without being as intrusive as a webcam feed. Discord Bots are also supremely easy to set up or invite to handle mood music, way less involved than for other platforms.
I've never used Hangouts for that purpose and generally dislike using Google stuff. It wants you to use your real name, it wants webcams by default which you're not going to want when you've got limited screen real estate. It's probably fine, but it's not going to be as dead simple as getting people using Discord, which doesn't even require an account to use, assuming you don't configure your server to require an account.